褶皱岩层初始挠曲的分叉特性     

杨成永  陈至达  杨锡禄 《大地测量与地球动力学》1995,(3)

基于拖带坐标法建立了岩层大变形的一维非线性微分方程，然后用解析与数值方法研究了变刚度、可伸缩岩层在侧向压力及自重作用下的分叉特性，初步揭示了褶皱岩层初始挠曲的形成机理。  相似文献   

Wolf-Rayet stars     

K. A. van der Hucht 《Astronomy and Astrophysics Review》1992,4(2):123-159

Summary Recent literature on Population I Wolf-Rayet star research extending from the Milky Way to blue compact dwarf galaxies is reviewed, broken down into inventory, basic parameters and galactic distribution, atmospheres, binaries, intrinsic variability, mass loss, enrichment and evolution. Also the incidence of Wolf-Rayet stars with variable non-thermal radio emission, excess X-ray fluxes, and episodic/periodic IR excesses is reviewed. These phenomena appear to be associated with wind-wind interaction in wide long-period WR+OB binaries and with wind-compact object interaction in WR+c binaries, with orbit sizes of the order of magnitude of the WR radio photosphere sizes or larger.  相似文献   

K-H Instability of Dust Plasma     

Shi Zhi-dong  Li Zhong-yuanUniversity of Science  Technology of China  Hefei    PRC Advanced Centre for Earth Science  Astronomy  Third World Academy of Science 《紫金山天文台台刊》1996,(2)

Areview about K-H instability related to comet tail is presented.The effect of dust graing on KHI is theoretically analysed and relations of critical shear to excit KHI with the properties of dust grains both for sheared ion flow and for sheared dust flow re put out.Their possible application in comet tail is suggested.  相似文献   

Yields of Nucleosynthesis from massive and intermediate mass stars and constraints on their final evolution     

D. C. V. Mallik  Sushma V. Mallik 《Journal of Astrophysics and Astronomy》1985,6(3):113-130

Nucleosynthetic yields and production rates of helium and heavy elements are derived using new initial mass functions which take into account the recent revisions in O star counts and the stellar models of Maeder (1981a, b) which incorporate the effects of massloss on evolution. The current production rates are significantly higher than the earlier results due to Chiosi & Caimmi (1979) and Chiosi (1979), and a near-uniform birthrate operating over the history of the galactic disc explains the currently observed abundances. However, the yields are incompatibly high, and to obtain agreement it is necessary to assume that stars above a certain mass do not explode but proceed to total collapse. Further confirmation of this idea comes from the consideration of the specific yields and production rates of oxygen, carbon and iron and the constraints imposed by the observational enrichment history in the disc as discussed by Twarog & Wheeler (1982). Substantial amounts of⁴He and¹⁴C, amongst the primary synthesis species, are contributed by the intermediate mass stars in their wind phases. If substantial numbers of them exploded as Type I SN, their contribution to the yields of¹²C and⁵⁶Fe would be far in excess of the requirements of galactic nucleosynthesis. Either efficient massloss precludes such catastrophic ends for these stars, or the current stellar models are sufficiently in error to leave room for substantial revisions in the specific yields. The proposed upward revision of the¹²C (α,γ)¹⁶O rate may produce the necessary changes in stellar yields to provide a solution to this problem. Stars that produce most of the metals in the Galaxy are the same ones that contribute most to the observed supernova rate.  相似文献   

Observations of hydrogen deficient binary Upsilon sagittarii     

N. Kameswara Rao  V. R. Venugopal 《Journal of Astrophysics and Astronomy》1985,6(2):101-112

The absolute magnitudeM _v of the hydrogen deficient binary υ Sgr has been estimated as -4.8 ± 1.0 from the distribution of the interstellar reddening, polarization and interstellar lines of the surrounding stars. From the ANS observations obtained at the time of the secondary eclipse, it appears that the hotter secondary is surrounded by a disc with colours of a B8-B9 star. The λ 1550 CIv absorption line arising in the stellar wind does not show any change in strength during the secondary minimum. The upper limit to the mass-loss rate from the high temperature wind is estimated as ≤ 5 × 10^-7 M⊙ yr^-1 from the 2 cm and 6 cm radio observations. Based on observations obtained with the Astronomical Netherlands Satellite and VLA. The National Radio Astronomy Observatory’s Very Large Array at Socorro, New Mexico is operated by Associated Universities Inc. under contract with the National Science Foundation.  相似文献   

UBV RI CCD photometric study of the open clusters Basel 4 and NGC 7067     

R. K. S. Yadav  Ram Sagar 《Monthly notices of the Royal Astronomical Society》2004,349(4):1481-1492

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CLIMATIC　TREND　INDICATED　BY　VARIATIONS　OF　GLACIERS　AND　LAKES　IN　THE　TIANSHAN　MOUNTAINS     

胡汝骥  杨川德  马虹  姜逢清 《中国地理科学(英文版)》1996,6(3):239-246

ＣＬＩＭＡＴＩＣＴＲＥＮＤＩＮＤＩＣＡＴＥＤＢＹＶＡＲＩＡＴＩＯＮＳＯＦＧＬＡＣＩＥＲＳＡＮＤＬＡＫＥＳＩＮＴＨＥＴＩＡＮＳＨＡＮＭＯＵＮＴＡＩＮＳ￥ＨｕＲｕｊｉ；ＹａｎｇＣｈｕａｎｄｅ；ＭａＨｏｎｇ；ＪｉａｎｇＦｅｎｇｑｉｎｇ（ＸｉｎｊｉａｎｇＩｎ...  相似文献   

AN INTEGRATED APPROACH TO AIR MASS CLASSIFICATION IN THE NORTH CENTRAL UNITED STATES     

Mark D. Schwartz 《The Professional geographer》1991,43(1):77-91

Both subjective and objective schemes for air mass classification offer advantages to climatological studies. An integrated approach is developed and applied to 850 mb level data in the north central United States. Each air mass type was initially delimited by a subjective analysis. Final limits were then determined with an objective technique that separates temperature curves into normal components based on interpretation from the subjective method. Continental air was most frequent in all seasons except summer. The methodology also allows estimation of classification error.  相似文献   

Upscaling of elastic properties for large scale geomechanical simulations     

F. Chalon  M. Mainguy  P. Longuemare  P. Lemonnier 《国际地质力学数值与分析法杂志》2004,28(11):1105-1119

Large scale geomechanical simulations are being increasingly used to model the compaction of stress dependent reservoirs, predict the long term integrity of under‐ground radioactive waste disposals, and analyse the viability of hot‐dry rock geothermal sites. These large scale simulations require the definition of homogenous mechanical properties for each geomechanical cell whereas the rock properties are expected to vary at a smaller scale. Therefore, this paper proposes a new methodology that makes possible to define the equivalent mechanical properties of the geomechanical cells using the fine scale information given in the geological model. This methodology is implemented on a synthetic reservoir case and two upscaling procedures providing the effective elastic properties of the Hooke's law are tested. The first upscaling procedure is an analytical method for perfectly stratified rock mass, whereas the second procedure computes lower and upper bounds of the equivalent properties with no assumption on the small scale heterogeneity distribution. Both procedures are applied to one geomechanical cell extracted from the reservoir structure. The results show that the analytical and numerical upscaling procedures provide accurate estimations of the effective parameters. Furthermore, a large scale simulation using the homogenized properties of each geomechanical cell calculated with the analytical method demonstrates that the overall behaviour of the reservoir structure is well reproduced for two different loading cases. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Simulation of double cold cores of the 35°N section in the Yellow Sea with a wave-tide-circulation coupled model   总被引：1，自引：0，他引：1  

Xia Changshui  Qiao Fangli  Zhang Mengning  Yang Yongzeng  Yuan Yeli 《中国海洋湖沼学报》2004,22(3):292-298

Based on the MASNUM wave-tide-circulation coupled numerical model, the temperature structure along 35°N in the Yellow Sea was simulated and compared with the observations. One of the notable features of the temperature structure along 35°N section is the double cold cores phenomena during spring and summer. The double cold cores refer to the two cold water centers located near 122°E and 125°E from the depth of 30m to bottom. The formation, maintenance and disappearance of the double cold cores are discussed. At least two reasons make the temperature in the center (near 123°E) of the section higher than that near the west and east shores in winter. One reason is that the water there is deeper than the west and east sides so its heat content is higher. The other is invasion of the warm water brought by the Yellow Sea Warm Current (YSWC) during winter. This temperature pattern of the lower layer (from 30m to bottom) is maintained through spring and summer when the upper layer (0 to 30m) is heated and strong thermocline is formed. Large zonal span of the 35°N section (about 600 km) makes the cold cores have more opportunity to survive. The double cold cores phenomena disappears in early autumn when the west cold core vanishes first with the dropping of the thermocline position. Supported by the National Basic Research Program of China (No. G1999043809) and the National Science Foundation of China (No. 49736190).  相似文献